Comb-Push Ultrasound Shear Elastography (CUSE): A Novel Method for Two-Dimensional Shear Elasticity Imaging of Soft Tissues

Fast and accurate tissue elasticity imaging is essential in studying dynamic tissue mechanical properties. Various ultrasound shear elasticity imaging techniques have been developed in the last two decades. However, to reconstruct a full field-of-view 2-D shear elasticity map, multiple data acquisitions are typically required. In this paper, a novel shear elasticity imaging technique, comb-push ultrasound shear elastography (CUSE), is introduced in which only one rapid data acquisition (less than 35 ms) is needed to reconstruct a full field-of-view 2-D shear wave speed map (40 × 38 mm). Multiple unfocused ultrasound beams arranged in a comb pattern (comb-push) are used to generate shear waves. A directional filter is then applied upon the shear wave field to extract the left-to-right (LR) and right-to-left (RL) propagating shear waves. Local shear wave speed is recovered using a time-of-flight method based on both LR and RL waves. Finally, a 2-D shear wave speed map is reconstructed by combining the LR and RL speed maps. Smooth and accurate shear wave speed maps are reconstructed using the proposed CUSE method in two calibrated homogeneous phantoms with different moduli. Inclusion phantom experiments demonstrate that CUSE is capable of providing good contrast (contrast-to-noise ratio ≥ 25 dB) between the inclusion and background without artifacts and is insensitive to inclusion positions. Safety measurements demonstrate that all regulated parameters of the ultrasound output level used in CUSE sequence are well below the FDA limits for diagnostic ultrasound.     

Antioxidant Extraction from Mustard (Brassica juncea) Seed Meal Using High‐Intensity Ultrasound

Brassicaceae oilseeds provide feedstocks for the biofuels industry, but value‐added coproducts are necessary to supply financial incentives for increased production. Our objective was to use high‐intensity ultrasound to optimize extraction of antioxidants from mustard (Brassica juncea) seed meal. The ultrasound‐assisted extraction (UAE) variables included temperature, solvent‐to‐material ratio, sonication duration, and EtOH concentration. Extracts were analyzed for total phenolics content (TPC), antioxidant activity, and sinapine content. Conventional extraction using water and 70% EtOH (v/v) at 80 °C for 3×30 min yielded 7.83 ± 0.07 and 8.81 ± 0.17 mg sinapic acid equivalents (SAE)/g meal, respectively. UAE extraction at 40 °C for 30 min yielded similar phenolics content (8.85 ± 0.33 mg SAE/g meal) as conventional hot ethanolic extraction, but required less time and lower temperature. The highest TPC (13.79 ± 0.38 mg SAE/g meal) was in the 7‐d aqueous extracts. Sonicated solutions of pure sinapine and sinapic acid showed 1st‐order reaction kinetics with greater degradation of isolated compounds than those present in extracts. Sinapine contained in extracts showed insignificant (P < 0.05) degradation after 30 min of sonication. Our research indicates that ultrasound treatment can assist the extraction of antioxidants from B. juncea meal by reducing both the temperature and time requirement without significant degradation of the primary antioxidants present.     

Clothing systems for outdoor activities

Participation in outdoor activities can improve mental, physical and social well-being. Such activities also present significant physiological strain and risks such as hypothermia; therefore, correct choice and usage of clothing is extremely important. The aim of this review is to critically analyse the literature regarding outdoor clothing systems, focusing on the layers comprising a typical clothing system. Additionally, alternative systems, potential improvements and future trends are discussed.     

Surface Energy and Adhesion Studies on Acrylic Pressure Sensitive Adhesives

The surface energy and adhesion dynamics of pressure sensitive adhesives-like networks (PSA-LNs) as mimics for PSAs were studied using JKR-based contact mechanics and peel tests. Acrylic acid (AA) was co-polymerized with 2-ethyl hexyl acrylate (2-EHA) and 1,6-hexane diol diacrylate (HDDA) to create PSA-LNs. The measured surface energy (27 to 31 mJ/m²) was sensible as surmised from their structure. Acrylic acid content increases the surface energy, threshold adhesion energy and adhesion hysteresis of PSA-LNs. Measurements of adhesion dynamics showed a dependence of adhesion energy to the 0.6-0.8 power of crack speed, depending upon the model chosen for analysis of the data. When compared with actual pressure-sensitive adhesive tape peel tests, the adhesion dynamics data predicted the peel strength. This study shows a direct relationship between threshold adhesion energy, crack propagation mechanics and peel strength measurements.     

Interfacial Energy and Adhesion between Acrylic Pressure Sensitive Adhesives and Release Coatings

The interfacial adhesive behavior between acrylic pressure sensitive adhesive-like networks (PSA-LNs) and poly(vinyl N-alkyl carbamate) release coatings was studied using a contact mechanical method and peel tests. Surface energy and interfacial energy were directly measured in JKR tests using a novel sample construction. The surface energy of the poly(vinyl N-alkyl carbamates) was found to be around 20 mJ/m². Interfacial energies between PSA-LNs and the release coatings were found to be quite high - between 7 and 24 mJ/m². Changes in adhesion dynamics were governed by acid-base interactions between the carbamate in the release coating and the acid groups in the PSA-LN. The length of the alkyl chain in the release coating moderated this effect. We also found a correlation between fundamental adhesion energy and peel strength. Examination of this phenomenon provides a basis for understanding the poor storage stability of PSA tapes made using alkyl carbamates and acid-containing PSAs.     

AC impedance investigation of conductivity of automotive lubricants using two- and four-electrode electrochemical cells

Two- and four-electrode electrochemical cells were designed for characterization studies of highly resistive non-aqueous automotive lubricant using electrochemical impedance spectroscopy (EIS). The influence of internal configuration of the impedance analyzer, the media’s temperature and properties, shielding of the cables, and the electrochemical cell geometry and arrangement on the impedance results were investigated. The most accurate EIS measurements can be made in the two-electrode configuration with active shields where a single arc at high frequencies and a complicated low frequency impedance feature were observed in complex impedance plots. When four-electrode cells were employed, the impedance load, geometry and positioning of voltage electrodes; finite resistance of the impedance analyzer; and capacitive coupling between the signal lines introduced two types of impedance measurement artifacts. A capacitive-resistive low frequency load was interpreted as a measurement artifact originating from geometry and positioning of voltage electrodes. The appearance of additional medium frequency load combining resistive, capacitive and inductive features is intrinsic to the measurement setup and is due to a combination of several instrumental and experimental factors resulting in a voltage divider effect.     

Liquid-liquid phase separation in a polyethylene blend monitored by crystallization kinetics and crystal-decorated phase morphologies

A series of polyethylene (PE) blends consisting of a linear high density polyethylene (HDPE) and a linear low density polyethylene (LLDPE) with an octane-chain branch density of 120/1000 carbon was prepared at different concentrations. The two components of this set of blends possessed isorefractive indices, thus, making it difficult to detect their liquid-liquid phase separation via scattering techniques. Above the experimentally observed melting temperature of HDPE, T_m = 133 °C, this series of blends can be considered to be in the liquid state. The LLDPE crystallization temperature was below 50 °C; therefore, above 80 °C and below the melting temperature of HDPE, a series of crystalline-amorphous PE blends could be created. A specifically designed two-step isothermal experimental procedure was utilized to monitor the liquid-liquid phase separation of this set of blends. The first step was to quench the system from temperatures of known miscibility and isothermally anneal them at a temperature higher than the equilibrium melting temperature of the HDPE for the purpose of allowing the phase morphology to develop from liquid-liquid phase separation. The second step was to quench the system to a temperature at which the HDPE could rapidly crystallize. The time for developing 50% of the total crystallinity (t_1/2) was used to monitor the crystallization kinetics. Because phase separation results in HDPE-rich domains where the crystallization rates are increased, this technique provided an experimental measure to identify the binodal curve of the liquid-liquid phase separation for the system indicated by faster t_1/2. The annealing temperature in the first step that exhibits an onset of the decrease in t_1/2 is the temperature of the binodal point for that blend composition. In addition, the HDPE-rich domains crystallized to form spherulites which decorate the phase-separated morphology. Therefore, the crystal dispersion indicates whether the phase separation followed a nucleation-and-growth process or a spinodal decomposition process. These crystal-decorated morphologies enabled the spinodal curve to be experimentally determined for the first time in this set of blends.     

Seamless, axially aligned, fiber tubes, meshes, microbundles and gradient biomaterial constructs

A new electrospinning apparatus was developed to generate nanofibrous materials with improved organizational control. The system functions by oscillating the deposition signal (ODS) of multiple collectors, allowing significantly improved nanofiber control by manipulating the electric field which drives the electrospinning process. Other electrospinning techniques designed to impart deposited fiber organizational control, such as rotating mandrels or parallel collector systems, do not generate seamless constructs with high quality alignment in sizes large enough for medical devices. In contrast, the ODS collection system produces deposited fiber networks with highly pure alignment in a variety of forms and sizes, including flat (8?×?8?cm²), tubular (1.3?cm diameter), or rope-like microbundle (45?μm diameter) samples. Additionally, the mechanism of our technique allows for scale-up beyond these dimensions. The ODS collection system produced 81.6?% of fibers aligned within 5° of the axial direction, nearly a four-fold improvement over the rotating mandrel technique. The meshes produced from the 9?% (w/v) fibroin/PEO blend demonstrated significant mechanical anisotropy due to the fiber alignment. In 37?°C PBS, aligned samples produced an ultimate tensile strength of 16.47?±?1.18?MPa, a Young’s modulus of 37.33?MPa, and a yield strength of 7.79?±?1.13?MPa. The material was 300?% stiffer when extended in the direction of fiber alignment and required 20 times the amount of force to be deformed, compared to aligned meshes extended perpendicular to the fiber direction. The ODS technique could be applied to any electrospinnable polymer to overcome the more limited uniformity and induced mechanical strain of rotating mandrel techniques, and greatly surpasses the limited length of standard parallel collector techniques.